This invention relates to gas turbine engines, and more particularly to combustion chambers for use therein.
Gas turbine engine efficiency is a function of various parameters, among them the temperature achievable within combustion chambers, as well as the amount of air which must be diverted to cool various elements of the engine. Contemporaneously, the structural integrity of an engine is improved if structural loads are carried by elements of the engine which elements are not also subjected to high temperatures and attendant thermal stresses.
In an attempt to raise achievable temperatures within combustion chambers, various materials and alloys have been used in the construction of the chambers. Two such materials which exhibit particularly beneficial thermal resistance are oxide dispersion strengthened metals such as thoria dispersed nickel and thoria dispersed nickel chromium alloy, which have melting temperatures of approximately 2500.degree. to 2600.degree. F., and which exhibit high strength characteristics up to temperatures of 2200.degree. F. Thus, these materials would prove successful in the construction of combustion chambers. A major drawback of these and certain other high temperatures materials, however, is that they are difficult or impractical to weld. A co-pending application, Ser. No. 316,531, now U.S. Pat. No. 4,480,436 and assigned to the common assignee, discloses an invention making possible the use of these and other appropriate materials in the construction of combustion chambers.
The effective application of such high temperature operating materials as those discussed, in addition to enabling higher temperatures to be reached, will also allow a reduction in the amount of cooling fluid required to be directed to the combustion chamber during operation. This reduction enables the engine to operate with increased efficiency. The present invention also provides means for more effectively utilizing a reduced quantity of cooling air to cool both the inner and outer sides of the combustion chamber liner.
Structural failures in gas turbine engines in the past have sometimes resulted from the subjection of structural load bearing portions of the engine to thermal stresses associated with the high temperatures of combustion. The formation of a combustion chamber in a way that requires the chamber liner (which is directly exposed to the heat of combustion) to carry structural loads associated with the combustion chamber has sometimes resulted in such failures. Use of the configuration of the present invention overcomes these problems by isolating the liner of the combustion chamber from the structural loads associated with the frame encircling the chamber.
Another significant facet of the present invention is that it permits the easy and efficient removal of individual liner panels without the necessity for total disassembly of the structural frame and associated components. This, in turn, permits the substitution of new liner panels for those which may have become worn over extended use, or the repair of individual liner panels which retain a useful life. Such a capability proves a great cost saving with respect to prior art devices wherein combustion chambers have been formed of substantially unitized construction and wherein damage or wear to a single portion of the chamber has necessitated the replacement of large sections thereof.